wil6210: Tx performance monitoring

For performance monitoring, trace time intervals when Tx vring
is idle/not idle. Use CPU cycle counter for this, because jiffies is
too rough, and other precise time measurement methods involve
overhead while get_cycles() should be fast.
This used to provide some estimation for percentage when Tx vring
was idle, i.e. when hardware is under-utilized.
Estimation is not precise because of many reasons - CPU frequency scaling,
grt_cycles() may be per core etc. But still, it is good estimation
Signed-off-by: Vladimir Kondratiev <qca_vkondrat@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/wil6210/debugfs.c

@@ -69,6 +69,8 @@ static int wil_vring_debugfs_show(struct seq_file *s, void *data)
 
 	for (i = 0; i < ARRAY_SIZE(wil->vring_tx); i++) {
 		struct vring *vring = &(wil->vring_tx[i]);
+		struct vring_tx_data *txdata = &wil->vring_tx_data[i];
+
 		if (vring->va) {
 			int cid = wil->vring2cid_tid[i][0];
 			int tid = wil->vring2cid_tid[i][1];
@@ -78,10 +80,20 @@ static int wil_vring_debugfs_show(struct seq_file *s, void *data)
 				   % vring->size;
 			int avail = vring->size - used - 1;
 			char name[10];
+			/* performance monitoring */
+			cycles_t now = get_cycles();
+			cycles_t idle = txdata->idle;
+			cycles_t total = now - txdata->begin;
+
+			txdata->begin = now;
+			txdata->idle = 0ULL;
+
 			snprintf(name, sizeof(name), "tx_%2d", i);
 
-			seq_printf(s, "\n%pM CID %d TID %d [%3d|%3d]\n",
-				   wil->sta[cid].addr, cid, tid, used, avail);
+			seq_printf(s, "\n%pM CID %d TID %d [%3d|%3d] idle %3d%%\n",
+				   wil->sta[cid].addr, cid, tid, used, avail,
+				   (int)((idle*100)/total));
+
 			wil_print_vring(s, wil, name, vring, '_', 'H');
 		}
 	}

drivers/net/wireless/ath/wil6210/txrx.c

@@ -881,6 +881,7 @@ static int wil_tx_vring(struct wil6210_priv *wil, struct vring *vring,
 	int nr_frags = skb_shinfo(skb)->nr_frags;
 	uint f = 0;
 	int vring_index = vring - wil->vring_tx;
+	struct vring_tx_data *txdata = &wil->vring_tx_data[vring_index];
 	uint i = swhead;
 	dma_addr_t pa;
 
@@ -953,6 +954,9 @@ static int wil_tx_vring(struct wil6210_priv *wil, struct vring *vring,
 	wil_hex_dump_txrx("Tx ", DUMP_PREFIX_NONE, 32, 4,
 			  (const void *)d, sizeof(*d), false);
 
+	if (wil_vring_is_empty(vring)) /* performance monitoring */
+		txdata->idle += get_cycles() - txdata->last_idle;
+
 	/* advance swhead */
 	wil_vring_advance_head(vring, nr_frags + 1);
 	wil_dbg_txrx(wil, "Tx swhead %d -> %d\n", swhead, vring->swhead);
@@ -1133,8 +1137,10 @@ int wil_tx_complete(struct wil6210_priv *wil, int ringid)
 		}
 	}
 
-	if (wil_vring_is_empty(vring))
+	if (wil_vring_is_empty(vring)) { /* performance monitoring */
 		wil_dbg_txrx(wil, "Ring[%2d] empty\n", ringid);
+		txdata->last_idle = get_cycles();
+	}
 
 	if (wil_vring_avail_tx(vring) > wil_vring_wmark_high(vring))
 		netif_tx_wake_all_queues(wil_to_ndev(wil));

drivers/net/wireless/ath/wil6210/wil6210.h

@@ -20,6 +20,7 @@
 #include <linux/netdevice.h>
 #include <linux/wireless.h>
 #include <net/cfg80211.h>
+#include <linux/timex.h>
 
 #define WIL_NAME "wil6210"
 
@@ -251,7 +252,7 @@ struct vring {
  */
 struct vring_tx_data {
 	int enabled;
-
+	cycles_t idle, last_idle, begin;
 };
 
 enum { /* for wil6210_priv.status */